| Full text | |
| Author(s): |
dos Santos, Angela Machado
[1]
;
Batista, Inez Staciarini
[1]
;
Abdu, Mangalathayil Ali
[1, 2]
;
Andrade Sobral, Jose Humberto
[1]
;
de Souza, Jonas Rodrigues
[1]
;
Marques Brum, Christiano Garnett
[3]
Total Authors: 6
|
| Affiliation: | [1] Natl Inst Space Res INPE, Aeron Div DIDAE, Sao Jose Dos Campos, SP - Brazil
[2] DCTA, Inst Tecnol Aeronaut, Sao Jose Dos Campos, SP - Brazil
[3] Univ Cent Florida, Arecibo Observ, Arecibo, PR - USA
Total Affiliations: 3
|
| Document type: | Journal article |
| Source: | Annales Geophysicae; v. 37, n. 6, p. 1005-1024, NOV 8 2019. |
| Web of Science Citations: | 0 |
| Abstract | |
In this work, we have performed a study for the first time on the climatology of the intermediate descending layers (ILs) over Brazilian equatorial and low-latitude regions during the extreme solar minimum period of 2009. The result of this study shows that the occurrence frequency of the ILs is very high, being > 60% over Sao Luis (2 degrees S, 44 degrees W; inclination: -3.8 degrees) and > 90% in Cachoeira Paulista (22.42 degrees S, 45 degrees W; inclination: -33.5 degrees). In most cases the ILs occur during the day at altitudes varying from 130 to 180 km and they may descend to lower altitudes (similar to 100 km) in a time interval of a few minutes to hours. The main driving force for the ILs at the low-latitude region, may be considered to be the diurnal tide (24 h) followed in smaller dominance by the semidiurnal (12 h), terdiurnal (8 h) and quarter-diurnal (6 h) components. In the magnetic equatorial sector, similar behavior was seen, with the exception of the semidiurnal tide, which in general does not appear to have influenced the IL's dynamics (except in summer). Additionally, the IL mean descent velocity over Sao Luis and Cachoeira Paulista shows a day-to-day variability that may be associated with a wave-like perturbation with a periodicity of some days. Some peculiarities in the IL dynamics were noted, such as the presence of the ILs during the night hours. Ascending and descending ILs appeared to have been formed from some connection with the ionospheric F layer. Quite often, these characteristics are observed in the presence of strong signatures of the gravity wave propagation as suggested by the F layer traces in the ionogram. The descending intermediate layer over Brazil appears to have been formed through a process of F1 layer base detachment. An interesting case study showed that an ascending ILs, initially detected at similar to 130 km, reached the base of the F2 layer, due probably to the gravity wave propagation and/or the effect of a prompt penetration electric field. (AU) | |
| FAPESP's process: | 15/25357-4 - Climatology of Intermediate Layers on the Equatorial and Low Latitudes Regions over Brazilian sector |
| Grantee: | Angela Machado dos Santos Valentim |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |